Organic electroluminescent device and luminescent material

ABSTRACT

An organic EL device is provided which is capable of providing high luminance and high luminous efficiency. In an organic EL device, a hole injecting electrode lies on a glass substrate, and a hole injecting layer, a hole transporting layer, and a light emitting layer are sequentially formed thereon. An electron injecting electrode lies on the light emitting layer. The light emitting layer contains a host material, a light emitting dopant, and a first light-emission assisting dopant. The first light-emission assisting dopant is composed of a rubrene derivative.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent deviceand luminescent material.

BACKGROUND ART

Organic electroluminescent devices (hereinafter referred to as organicEL devices) are new self-emitting devices of great prospects. Theorganic EL devices have a stacked structure in which a carriertransporting layer (an electron or hole transporting layer) and a lightemitting layer are sandwiched between a hole injecting electrode and anelectron injecting electrode.

An electrode material having a large work function, such as gold or ITO(indium-tin oxide), is used to form the hole injecting electrode, and anelectrode material having a small work function, such as Mg (magnesium)or Li (lithium), is used to form the electron injecting electrode.

The hole transporting layer, light emitting layer, and electrontransporting layer are formed of organic materials. A material havingp-type semiconductor properties is used to form the hole transportinglayer and a material having n-type semiconductor properties is used toform the electron transporting layer. The light emitting layer is formedof a fluorescent or phosphorescent organic material which, too, has acarrier transporting property, as an electron or hole transportingproperty.

The hole injecting electrode, hole transporting layer, light emittinglayer, electron transporting layer, and electron injecting electrode arestacked in this order to form an organic EL device.

The functional layers, i.e. the hole transporting layer, electrontransporting layer, and light emitting layer, may each be composed of aplurality of layers, or may be omitted, depending on the organicmaterials used.

For example, Chihaya Adachi et al., Appl. Phys. Lett., Vol. 55, pp.1489-1491 (1989) discloses a device structure that has only two organiclayers, light emitting and electron transporting layers, between thehole injecting electrode and electron injecting electrode. In thisdevice, the light emitting layer made of a luminescent material calledNSD has a good hole transporting property, so that the light emittinglayer can act also as a hole transporting layer.

C. W. Tang et al., Appl. Phys. Lett., Vol. 51, pp. 913-915 (1987)discloses a device structure that has two organic layers: holetransporting and light emitting layers. In this case,tris(8-hydroxyquinolinato)aluminum (hereinafter referred to as Alq) inthe light emitting layer performs two functions: light emitting andelectron transporting functions.

S. A. VanSlyke et al., Appl. Phys. Lett., Vol. 69, pp. 2160-2162 (1996)discloses a device structure that has three organic layers: a holeinjecting layer, hole transporting layer, and light emitting layer. Inthis case, the hole injecting layer, made of copper phthalocyanine,serves like a hole transporting layer; thus the entire device includestwo hole transporting layers.

In this way, the stacked structure of the electron transporting layer,hole transporting layer and light emitting layer can be freely designed,depending on the organic materials used.

Organic EL devices can be used to obtain visible light from blue to red,by properly selecting organic material of the light emitting layer.Therefore a full-color display can be implemented by using monochromaticorganic EL devices individually emitting red, green or blue light, i.e.the three primary colors of light (RGB).

Among red, green and blue lights obtained with organic EL devices, greenlight and blue light are stable. On the other hand, it is difficult toobtain light with high luminance and high luminous efficiency in therange from red to orange. Therefore developing full-color displaysrequires red-emitting organic EL devices with good color purity, highluminous efficiency, and high luminance.

JP2000-164362, A suggests a method in which rubrene having the molecularstructure represented by Formula (15) below is used as a light-emissionassisting dopant. While this method offers improved red color purity, itfails to provide sufficient luminous efficiency and sufficientluminance.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide an organic EL device capable ofproviding high luminance and high luminous efficiency.

Another object of the invention is to provide a luminescent materialcapable of providing high luminance and high luminous efficiency.

According to one aspect of the invention, an organic electroluminescentdevice includes a hole injecting electrode, an electron injectingelectrode, and a light emitting layer provided between the holeinjecting electrode and the electron injecting electrode, wherein thelight emitting layer contains a rubrene derivative having a molecularstructure represented by Formula (1):

wherein R11-R15, R21-R25, R31-R35 and R41-R45 are the same or differentand each represent a hydrogen atom or a substituent, where the structurein which all are hydrogen atoms is excluded. Adjacent two of R11-R15,adjacent two of R21-R25, adjacent two of R31-R35, and adjacent two ofR41-R45 may be bonded together to form rings. Adjacent three of R11-R15,adjacent three of R21-R25, adjacent three of R31-R35, and adjacent threeof R41-R45 may be bonded together to form rings.

Because the light emitting layer contains a rubrene derivative having amolecular structure represented by Formula (1), the organicelectroluminescent device of the invention provides high luminance andhigh luminous efficiency.

According to another aspect of the invention, an organicelectroluminescent device includes a hole injecting electrode, anelectron injecting electrode, and a light emitting layer providedbetween the hole injecting electrode and the electron injectingelectrode, wherein the light emitting layer contains a rubrenederivative having a molecular structure represented by Formula (2):

wherein R11-R15 and R21-R25 are the same or different and each representa hydrogen atom or a substituent. Adjacent two of R11-R15 and adjacenttwo of R21-R25 may be bonded together to form rings. Adjacent three ofR11-R15 and adjacent three of R21-R25 may be bonded together to formrings.

Because the light emitting layer contains a rubrene derivative having amolecular structure represented by Formula (2), the organicelectroluminescent device of the invention provides high luminance andhigh luminous efficiency.

According to still another aspect of the invention, an organicelectroluminescent device includes a hole injecting electrode, anelectron injecting electrode, and a light emitting layer providedbetween the hole injecting electrode and the electron injectingelectrode, wherein the light emitting layer contains a rubrenederivative having a molecular structure represented by Formula (3):

wherein Ar1-Ar6 are the same or different and each represent a hydrogenatom or a substituent. R1 and R2 are the same or different and eachrepresent a hydrogen atom or a substituent. Adjacent R1 and R2 may bebonded together to form a ring.

Because the light emitting layer contains a rubrene derivative having amolecular structure represented by Formula (3), the organicelectroluminescent device of the invention provides high luminance andhigh luminous efficiency.

According to a further aspect of the invention, an organicelectroluminescent device includes a hole injecting electrode, anelectron injecting electrode, and a light emitting layer providedbetween the hole injecting electrode and the electron injectingelectrode, wherein the light emitting layer contains a rubrenederivative having a molecular structure represented by Formula (4):

wherein Ar1-Ar10 are the same or different and each represent a hydrogenatom or a substituent.

Because the light emitting layer contains a rubrene derivative having amolecular structure represented by Formula (4), the organicelectroluminescent device of the invention provides high luminance andhigh luminous efficiency.

The rubrene derivative may be5,6,11,12-tetrakis(naphth-2-yl)-naphthacene having a molecular structurerepresented by Formula (A1):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be5,12-bis(4-(6-methylbenzothiazole-2-yl)phenyl)-6,11-diphenylnaphthacenerepresented by Formula (A2):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be5,6,11,12-tetrakis(4-tert-butylphenyl)-naphthacene represented byFormula (A3):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be 5,12-bis(4-tert-butylphenyl)-naphthacenerepresented by Formula (A4):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be 5,12-diphenylnaphthacene represented byFormula (A5):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be 5,12-bis(naphth-2-yl)-naphthacenerepresented by Formula (A6):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be 5,12-bis(pyrene-1-yl)-naphthacenerepresented by Formula (A7):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be 5,6,13,14-6-tetrakisphenyl-pentacenerepresented by Formula (A8):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be6,13-bis(4-(6-methylbenzothiazole-2-yl)phenyl)-pentacene represented byFormula (A9):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The rubrene derivative may be5,6,11,12-tetrakisphenyl-1,2-benzo-(3,4-benzo-)naphthacene representedby Formula (A10):

This enables higher luminance and higher luminous efficiency than whenthe light emitting layer contains rubrene.

The light emitting layer may contain a host material, a light emittingdopant, and a first light-emission assisting dopant, with the firstlight-emission assisting dopant being composed of a rubrene derivative.The first light-emission assisting dopant serves to transfer excitationenergy to the light emitting dopant. Using any of the rubrenederivatives shown above as the first light-emission assisting dopantenhances the luminance and luminous efficiency.

The light emitting layer may further contain a second light-emissionassisting dopant. The second light-emission assisting dopant serves toadjust the balance of carriers flowing in the light emitting layer.Using the second light-emission assisting dopant further enhances theluminance and luminous efficiency.

The light emitting layer may contain a host material and a lightemitting dopant, with the light emitting dopant being composed of arubrene derivative. Using any of the rubrene derivatives shown above asthe light emitting dopant enhances the luminance and luminousefficiency.

The content of the light emitting dopant may be not less than 0.1percent by weight nor more than 50 percent by weight, with respect tothe host material. This causes the light emitting dopant to act not as ahost but as a dopant.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C1) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C2) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C3) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C4) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C5) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C6) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C7) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C8) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C9) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C10) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C11) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C12) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C13) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C14) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C15) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C16) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C17) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C18) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C19) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

In an organic electroluminescent device having a light emitting layerbetween a hole injecting electrode and an electron injecting electrode,the light emitting layer may include a first light emitting layer thatcontains a compound having a molecular structure represented by Formula(C20) and a second light emitting layer that contains a luminescentmaterial that emits blue light.

The luminescent materials having the molecular structures represented byFormulas (C1)-(C20) are capable of emitting orange or yellow light withhigh luminance and high luminous efficiency, and so the first lightemitting layer emits orange or yellow light and the second lightemitting layer emits blue light. Then, because of the complementaryrelation between orange or yellow and blue, the organicelectroluminescent device is capable of emitting white light.

Preferably, the second light emitting layer contains an anthracenederivative as a host material and a perylene derivative as a lightemitting dopant. This allows the second light emitting layer toefficiently emit blue light.

In an organic electroluminescent device having a light emitting layerprovided between a hole injecting electrode and an electron injectingelectrode, the light emitting layer may include a first light emittinglayer that contains at least one compound selected from the groupconsisting of compounds having molecular structures represented byFormulas (C1)-(C20) and at least one compound selected from the groupconsisting of compounds represented by Formulas (A4)-(A7), (A10), and(C21)-(C27), and a second light emitting layer that contains aluminescent material that emits blue light.

The compounds having the molecular structures represented by Formulas(C1)-(C20) are capable of emitting orange light and the luminescentmaterials having the molecular structures represented by Formulas(A4)-(A7), (A10) and (C21)-(C27) are capable of emitting green light.Thus, when the first light emitting layer contains an orange-emittingluminescent material and a green-emitting luminescent material and thesecond light emitting layer contains a blue-emitting luminescentmaterial, it is possible to obtain high luminous efficiency and whitelight emission with high color purity.

According to still another aspect of the invention, a luminescentmaterial has a molecular structure represented by Formula (1):

wherein R11-R15, R21-R25, R31-R35 and R41-R45 are the same or differentand each represent a hydrogen atom or a substituent, where the structurein which all are hydrogen atoms is excluded. Adjacent two of R11-R15,adjacent two of R21-R25, adjacent two of R31-R35, and adjacent two ofR41-R45 may be bonded together to form rings. Adjacent three of R11-R15,adjacent three of R21-R25, adjacent three of R31-R35, and adjacent threeof R41-R45 may be bonded together to form rings.

According to a further aspect of the invention, a luminescent materialhas a molecular structure represented by Formula (2):

wherein R11-R15 and R21-R25 are the same or different and each representa hydrogen atom or a substituent. Adjacent two of R11-R15 and adjacenttwo of R21-R25 may be bonded together to form rings. Adjacent three ofR11-R15 and adjacent three of R21-R25 may be bonded together to formrings.

According to a further aspect of the invention, a luminescent materialhas a molecular structure represented by Formula (3):

wherein Ar1-Ar6 are the same or different and each represent a hydrogenatom or a substituent. R1 and R2 are the same or different and eachrepresent a hydrogen atom or a substituent. Adjacent R1 and R2 may bebonded together to form a ring.

According to a further aspect of the invention, a luminescent materialhas a molecular structure represented by Formula (4):

wherein Ar1-Ar10 are the same or different and each represent a hydrogenatom or a substituent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the structure of an organic ELdevice according to an embodiment of the invention; and

FIG. 2 is a schematic diagram showing the structure of an organic ELdevice according to another embodiment of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a schematic diagram showing the structure of an organicelectroluminescent device (hereinafter referred to as an organic ELdevice) according to an embodiment of the invention.

As shown in FIG. 1, in the organic EL device 100, a hole injectingelectrode (anode) 2, made of a transparent electrode film, resides on aglass substrate 1. On the hole injecting electrode 2, a hole injectinglayer 3 made of an organic material, a hole transporting layer 4 of anorganic material, and a light emitting layer 5 of an organic materialare formed in sequence. An electron injecting electrode (cathode) 6 lieson the light emitting layer 5. In place of the hole transporting layer4, an electron transporting layer may be provided between the lightemitting layer 5 and the electron injecting electrode 6.

It is preferred that the light emitting layer 5 contain a rubrenederivative having a molecular structure represented by Formula (1)below, or a rubrene derivative having a molecular structure representedby Formula (2) below.

In Formulas (1) and (2), R11-R15, R21-R25, R31-R35 and R41-R45 are thesame or different and each represent a hydrogen atom or a substituent,excepting for structures in which all are hydrogen atoms. Adjacent twoof R11-R15, adjacent two of R21-R25, adjacent two of R31-R35, andadjacent two of R41-R45 may be bonded together to form rings. Adjacentthree of R11-R15, adjacent three of R21-R25, adjacent three of R31-R35,and adjacent three of R41-R45 may be bonded together to form rings.

In Formula (2), R11-R15 and R21-R25 are the same or different and eachrepresent a hydrogen atom or a substituent. Adjacent two of R11-R15 andadjacent two of R21-R25 may be bonded together to form rings. Adjacentthree of R11-R15 and adjacent three of R21-R25 may be bonded together toform rings.

For example, in Formulas (1) and (2), R11-R15, R21-R25, R31-R35 andR41-R45 are —H, —C_(n)H_(2n+1) (n=1-10), —OC_(n)H_(2n+1) (n=1-10),—N(C_(n)H₂₊₁)₂ (n=1-10), —X (X═F, Cl, Br, or I), —CN, or substituentsrepresented by Formula (a1) below.

Note that the structure in which R11-R15, R21-R25, R31-R35, R41-R45 inFormula (1) are all —H is excluded. In Formula (a1), Y is O or S, forexample, and R′ is —H, —C_(n)H_(2n+1) (n=1-10), —OC_(n)H_(2n+1)(n=1-10), —N(C_(n)H_(2n+1))₂ (n=1-10), —X (X═F, Cl, Br, or I), —CN, or aphenyl group, for example.

In Formulas (1) and (2), adjacent two of R11-R15, adjacent two ofR21-R25, adjacent two of R31-R35, and adjacent two of R41-R45 may bebonded together to form any of the ring structures represented byFormula (a2) below.

In Formulas (1) and (2), adjacent three of R11-R15, adjacent three ofR21-R25, adjacent three of R31-R35, and adjacent three of R41-R45 may bebonded together to form the ring structure represented by Formula (a3)below.

Alternatively, the light emitting layer 5 preferably contains a rubrenederivative having a molecular structure represented by Formula (3)below, or a rubrene derivative having a molecular structure representedby Formula (4) below.

In Formulas (3) and (4), Ar1-Ar10 are the same or different and eachrepresent a hydrogen atom or a substituent. In Formula (3), R1 and R2are the same or different and each represent a hydrogen atom or asubstituent. In Formula (3), adjacent R1 and R2 may be bonded togetherto form a ring.

For example, in Formula (3), Ar1-Ar6 are —H, —C_(n)H_(2n+1) (n=1-10),—OC_(n)H_(2n+1) (n=1-10), —N(C_(n)H_(2n+1))₂ (n=1-10), —X (X═F, Cl, Br,or I), —CN, or any of substituents represented by Formula (a4).

In Formula (a4), R is, for example, —H, —C_(n)H_(2n+1) (n=1-10),—OC_(n)H_(2n+1) (n=1-10), —N(C_(n)H_(2n+1))₂ (n=1-10), —X (X═F, Cl, Br,or I), —CN, a phenyl group, or a substituent represented by Formula(a5).

In Formula (a5), Y is O or S, for example, and R′ is —H, —C_(n)H_(2n+1)(n=1-10), —OC_(n)H_(2n+1) (n=1-10), —N(C_(n)H_(2n+1))₂ (n=1-10), —X(X═F, Cl, Br, or I), —CN, or a phenyl group, for example.

In Formula (3), adjacent R1 and R2 may be bonded together to form any ofthe ring structures represented by Formula (a6) below.

In a first example, the light emitting layer 5 contains a host material,a light emitting dopant, and a first light-emission assisting dopant,where the first light-emission assisting dopant is composed of any ofthe rubrene derivatives shown above. The first light-emission assistingdopant serves to transfer excitation energy to the light emittingdopant. Using the rubrene derivatives shown above as the firstlight-emission assisting dopant enhances the luminance and luminousefficiency.

In a second example, the light emitting layer 5 contains a hostmaterial, a light emitting dopant, a first light-emission assistingdopant, and a second light-emission assisting dopant, where the firstlight-emission assisting dopant is composed of any of the rubrenederivatives shown above. The second light-emission assisting dopantserves to adjust the balance of carriers that flow in the light emittinglayer. Further adding the second light-emission assisting dopantenhances the luminance and luminous efficiency.

The first and second light-emission assisting dopants do not emit lightthemselves.

In a third example, the light emitting layer 5 contains a host materialand a light emitting dopant, where the light emitting dopant is composedof any of the rubrene derivatives shown above. Using the rubrenederivatives shown above as the light emitting dopant enhances theluminance and luminous efficiency.

In the cases above, the content of the light emitting dopant is from 0.1to 50 percent by weight, preferably from 1 to 10 percent by weight, withrespect to the host material.

In the organic EL device 100, a voltage is applied between the holeinjecting electrode 2 and the electron injecting electrode 6 to causethe light emitting layer 5 in the organic EL device 100 to emit light,which is emitted from the back of the glass substrate 1.

Compounds represented by Formulas (1) to (4) can be prepared byconventional methods. For example, they can be obtained by couplingreactions, in the presence of transition metal compounds (e.g. palladiumcompounds), between condensed polycyclic hydrocarbons (e.g. naphthacene,pentacene, benz[a]naphthacene, dibenz[a,c]naphthacene, etc.) that haveleaving groups (e.g. halogen atoms) at certain positions and that haveadjacent benzene rings ortho-condensed, and compounds corresponding tosubstituents of the condensed polycyclic hydrocarbons (benzene compoundshaving R11-R45, compounds corresponding to Ar1-Ar10). Further, thereactions may be caused in a presence of bases (e.g. sodium hydroxide).The reactions can usually be carried out using an inert solvent in aninert gas atmosphere at about 30 to 120° C.

FIG. 2 is a schematic diagram showing the structure of an organic ELdevice according to another embodiment of the invention.

As shown in FIG. 2, in the organic EL device 100 a, a hole injectingelectrode (anode) 2, made of a transparent electrode film, resides on aglass substrate 1. On the hole injecting electrode 2, a hole injectinglayer 3 made of an organic material, a hole transporting layer 4 of anorganic material, a first light emitting layer 5 a of an organicmaterial, a second light emitting layer 5 b, and an electrontransporting layer 7 are formed in sequence. An electron injectingelectrode (cathode) 6 lies on the electron transporting layer 7.

The first light emitting layer 5 a contains a rubrene derivative thatemits orange or yellow light, among rubrene derivatives having molecularstructures represented by Formula (1) shown above, rubrene derivativeshaving molecular structures represented by Formula (2) above, rubrenederivatives having molecular structures represented by Formula (3)above, or among rubrene derivatives having molecular structuresrepresented by Formula (4) above.

The second light emitting layer 5 b contains a luminescent material thatemits blue light. For example, the second light emitting layer 5 bcontains an anthracene derivative as a host material and contains aperylene derivative as a light emitting dopant.

For example, dianthranylanthracene having the molecular structure ofFormula (B1) can be used as an anthracene derivative.

Also, as an anthracene derivative, diphenylanthracene having themolecular structure of Formula (B2) may be used.

As for a perylene derivative, perylene having the molecular structure ofFormula (B3) can be used.

In the organic EL device 100 a of this embodiment, the first lightemitting layer 5 a emits orange or yellow light and the second lightemitting layer 5 b emits blue light. Thus, the organic EL device 100 acan emit white light, because of complementary relation between orangeor yellow and blue.

The first light emitting layer 5 a may be doped with light emittingdopants of two kinds: an orange-emitting rubrene derivative (forexample, any of the rubrene derivatives represented by Formulas (C1) to(C20) shown later) and a green-emitting rubrene derivative (for example,any of the rubrene derivatives represented by Formulas (A4) to (A7),(A10) and (C21) to (C27) shown later). This enhances luminous efficiencyof white, and also enhances color purity of white since the halfbandwidth of the spectrum increases.

EXAMPLES

(1) First, organic EL devices of Examples 1 to 33 and Examples forComparison, 1 to 5, were constructed and luminescence characteristics ofthese devices were measured.

Organic EL devices of Examples 1-10 and Comparative Example 1 haveDevice Structure A, organic EL devices of Examples 11-22 and ComparativeExample 2 have Device Structure B, organic EL devices of Examples 23-28and Comparative Examples 3-5 have Device Structure C, and organic ELdevices of Examples 29-33 have Device Structure D.

In particular, rubrene derivatives having the molecular structures ofFormulas (A1)-(A10) below were used as materials of the light emittinglayer.

5,6,11,12-tetrakis(naphth-2-yl)-naphthacene (hereinafter referred to asTNN):

5,12-bis(4-(6-methylbenzothiazole-2-yl)phenyl)-6,11-diphenylnaphthacene(hereinafter referred to as DBZR):

5,6,11,12-tetrakis(4-tert-butylphenyl)-naphthacene (hereinafter referredto as TtBuPN):

5,12-bis(4-tert-butylphenyl)-naphthacene (hereinafter referred to asDtBuPN):

5,12-diphenylnaphthacene (hereinafter referred to as DPN):

5,12-bis(naphth-2-yl)-naphthacene(hereinafter referred to as DNN):

5,12-bis(pyrene-1-yl)-naphthacene(hereinafter referred to as DPyN):

5,6,13,14-6-tetrakisphenyl-pentacene (hereinafter referred to as TPhP):

6,13-bis(4-(6-methylbenzothiazole-2-yl)phenyl)-pentacene (hereinafterreferred to as DBZP):

5,6,11,12-tetrakisphenyl-1,2-benzo-(3,4-benzo-)naphthacene (hereinafterreferred to as TPh-DBN):

(A) Device Structure A

In Device Structure A, a hole injecting electrode (anode), a holeinjecting layer, a hole transporting layer, a light emitting layer, andan electron injecting electrode (cathode) are sequentially stacked on aglass substrate.

In this case, the hole injecting electrode of the organic EL device hasa thickness of 1000 Å and is formed of indium-tin oxide (ITO). The holeinjecting layer has a thickness of 500 Å and is formed of4,4′,4″-Tris(N-(2-naphthyl)-N-phenyl-amino)-triphenylamine (hereinafterreferred to as 2TNATA) having the molecular structure represented byFormula (22) below.

The hole transporting layer has a thickness of 150 Å and is formed ofN,N′-Di(naphthalen-1-yl)-N,N′-diphenyl-benzidine (hereinafter referredto as NPB) having the molecular structure of Formula (23).

The light emitting layer has a thickness of 500 Å, and contains, as ahost material, Tris(8-hydroxyquinolinato)aluminum (hereinafter referredto as Alq) having the molecular structure of Formula (24) below, andcontains, as a red light emitting dopant, 2% of2-(1,1-Dimethylethyl)-6-(2-(2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1II,5II-benzo[ij]quinolizin-9-yl)ethenyl)-4H-pyran-4-ylidene)propanedinitrile(hereinafter referred to as DCJTB) having the molecular structure ofFormula (25), and also contains, as a first light-emission assistingdopant, 5% of a rubrene derivative, or one of those shown above.

The electron injecting electrode is formed of a MgIn alloy (a ratio of10:1) with a thickness of 2000 Å.

Examples 1-10 used, as first light-emission assisting dopants, DtBuPN,DPN, DNN, TNN, DBzR, DPyN, TtBuPN, DBZP, TPhP, and TPh-DBN,respectively. Comparative Example 1 used rubrene as a firstlight-emission assisting dopant.

(B) Device Structure B

In Device Structure B, a hole injecting electrode (anode), a holeinjecting layer, a hole transporting layer, a light emitting layer, andan electron injecting electrode (cathode) are sequentially stacked on aglass substrate.

In this case, the hole injecting electrode of the organic EL device hasa thickness of 1000 Å and is formed of indium-tin oxide (ITO). The holeinjecting layer has a thickness of 500 Å and is formed of 2TNATA. Thehole transporting layer has a thickness of 150 Å and is formed of NPB.

The light emitting layer has a thickness of 500 Å, and contains Alq as ahost material, 2% of DCJTB as a red-emitting dopant, 5% of a rubrenederivative, one of the rubrene derivatives shown above, as a firstlight-emission assisting dopant, and also contains, as a secondlight-emission assisting dopant, 6% of 4,4-Bis(carbazol-9-yl)-biphenyl(hereinafter referred to as CBP) having the molecular structure ofFormula (26), or N,N′-Bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine(hereinafter referred to as TPD) having the molecular structure ofFormula (27) below, or NPB.

The electron injecting electrode has a thickness of 2000 Å and is formedof a MgIn alloy (with a ratio of 10:1).

Examples 11-20 used, as first light-emission assisting dopants, DtBuPN,DPN, DNN, TNN, DBzR, DPyN, TtBuPN, DBzP, TPhP, and TPh-DBN,respectively. Comparative Example used rubrene as the firstlight-emission assisting dopant.

Example 21 used DtBuPN as the first light-emission assisting dopant andTPD as the second light-emission assisting dopant. Example 22 used DPNas the first light-emission assisting dopant and NPB as the secondlight-emission assisting dopant.

(C) Device Structure C

In Device Structure C, a hole injecting electrode (anode), a holeinjecting layer, a hole transporting layer, a light emitting layer, andan electron injecting electrode (cathode) are sequentially stacked on aglass substrate.

In this case, the hole injecting electrode of the organic EL device hasa thickness of 1000 Å and is formed of indium-tin oxide (ITO). The holeinjecting layer has a thickness of 500 Å and is formed of 2TNATA. Thehole transporting layer has a thickness of 150 Å and is formed of NPB.

The light emitting layer has a thickness of 500 Å, and contains Alq as ahost material, and 5% of a rubrene derivative, one of those shown above,as a light emitting dopant.

The electron injecting electrode is formed of a MgIn alloy (a ratio of10:1) with a thickness of 2000 Å.

Examples 23-28 used, as the light emitting dopants, DtBuPN, DPN, DNN,TNN, DBzR, and DPyN, respectively. Comparative Examples 3-5 respectivelyused, as light emitting dopants, Coumarin6 (or3-(2-Benzothiazolyl)-7-(diethylamino)coumarin) having the molecularstructure of Formula (28), rubrene, and4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran(hereinafter referred to as DCM) having the molecular structure ofFormula (29).

(D) Device Structure D

In Device Structure D, a hole injecting electrode (anode), a holeinjecting layer, a hole transporting layer, a light emitting layer, anelectron transporting layer, and an electron injecting electrode(cathode) are sequentially stacked on a glass substrate.

In this case, the hole injecting electrode of the organic EL device isformed of indium-tin oxide (ITO) with a thickness of 1000 Å. The holeinjecting layer has a thickness of 500 Å and is formed of 2TNATA.

The light emitting layer has a thickness of 150 Å, and contains NPB as ahost material, and 5% of a rubrene derivative, one of those shown above,as a light emitting dopant.

The electron transporting layer has a thickness of 500 Å and is formedof Alq. The electron injecting electrode is formed of MgIn alloy (aratio of 10:1) with a thickness of 2000 Å.

Examples 29-33 used, as the light emitting dopants, DtBuPN, DPN, DNN,TNN, and DBzR, respectively.

A positive bias voltage was applied to the hole injecting electrode ofeach organic EL device and a negative bias voltage was applied to theelectron injecting electrode, and luminescence characteristics of thedevices were measured.

Table 1 shows measurements of luminescence characteristics of theorganic EL devices of Examples 1-10 and Comparative Example 1.

TABLE 1 1st 2nd LUMINOUS LIGHT- LIGHT- EFFI- DEVICE LIGHT EMISSIONEMISSION EMITTED CIENCY WAVE- MAX STRUC- EMITTING ASSISTING ASSISTINGCOLOR (cd/A) LENGTH LUMINANCE TURE HOST DOPANT DOPANT DOPANT (CIEx, y)At100 cd/m² (nm) (cd/m²) EX. 1 A Alq DCJTB DtBuPN — Red 1.1 633 8,050 x= 0.65, y = 0.35 EX. 2 A Alq DCJTB DPN — Red 1.6 632 10,100 x = 0.65, y= 0.35 EX. 3 A Alq DCJTB DNN — Red 1.1 633 7,960 x = 0.65, y = 0.35 EX.4 A Alq DCJTB TNN — Red 1.4 633 9,030 x = 0.65, y = 0.35 EX. 5 A AlqDCJTB DBzR — Red 1.5 634 9,500 x = 0.65, y = 0.35 EX. 6 A Alq DCJTB DPyN— Red 1.1 635 7,900 x = 0.65, y = 0.35 EX. 7 A Alq DCJTB TtBuPN — Red1.5 634 9,600 x = 0.65, y = 0.35 EX. 8 A Alq DCJTB DBzP — Red 1.1 6377,600 x = 0.65, y = 0.35 EX. 9 A Alq DCJTB TPhP — Red 1.1 635 7,400 x =0.65, y = 0.35 EX. 10 A Alq DCJTB TPh-DBN — Red 1.1 635 7,700 x = 0.65,y = 0.35 Comparison 1 A Alq DCJTB Rubrene — Red 1.0 635 7,300 x = 0.65,y = 0.35

As shown in Table 1, the organic EL devices of Examples 1-10 andComparative Example 1 all provided red light emission with high colorpurity. The organic EL devices of Examples 1-10 provided higher luminousefficiency and higher maximum luminance than the organic EL device ofComparative Example 1. This shows that the use of the rubrenederivatives as the first light-emission assisting dopants is effectivein enhancing the luminous efficiency and maximum luminance.

Table 2 shows measurements of luminescence characteristics of theorganic EL devices of Examples 11-20 and Comparative Example 2.

TABLE 2 1st 2nd LUMINOUS LIGHT- LIGHT- EFFI- DEVICE LIGHT EMISSIONEMISSION EMITTED CIENCY WAVE- MAX STRUC- EMITTING ASSISTING ASSISTINGCOLOR (cd/A) LENGTH LUMINANCE TURE HOST DOPANT DOPANT DOPANT (CIEx, y)At100 cd/m² (nm) (cd/m²) EX. 11 B Alq DCJTB DtBuPN CBP Red 2.1 63414,450 x = 0.65, y = 0.35 EX. 12 B Alq DCJTB DPN CBP Red 2.7 632 18,100x = 0.65, y = 0.35 EX. 13 B Alq DCJTB DNN CBP Red 2.1 634 13,660 x =0.65, y = 0.35 EX. 14 B Alq DCJTB TNN CBP Red 2.5 634 15,080 x = 0.65, y= 0.35 EX. 15 B Alq DCJTB DBzR CBP Red 2.5 635 16,100 x = 0.65, y = 0.35EX. 16 B Alq DCJTB DPyN CBP Red 2.1 635 7,900 x = 0.65, y = 0.35 EX. 17B Alq DCJTB TtBuPN CBP Red 2.5 634 15,000 x = 0.65, y = 0.35 EX. 18 BAlq DCJTB DBzP CBP Red 2.1 637 8,100 x = 0.65, y = 0.35 EX. 19 B AlqDCJTB TPhP CBP Red 2.1 635 8,200 x = 0.65, y = 0.35 EX. 20 B Alq DCJTBTPh-DBN CBP Red 2.1 635 8,100 x = 0.65, y = 0.35 Comparison 2 B AlqDCJTB Rubrene CBP Red 2.0 634 12,820 x = 0.65, y = 0.35

As shown in Table 2, the organic EL devices of Examples 11-20 andComparative Example 2 all provided red light emission with high colorpurity. With the organic EL devices of Examples 11-20, the addition ofthe second light-emission assisting dopant enabled higher luminousefficiency and higher maximum luminance than those of the organic ELdevices of Examples 1-11. This shows that the addition of the secondlight-emission assisting dopant is effective in enhancing the luminousefficiency and maximum luminance. The organic EL devices of Examples11-20 provided higher luminous efficiency than the organic EL device ofExample 2. This shows that using the rubrene derivatives as the firstlight-emission assisting dopants is effective in enhancing the luminousefficiency and maximum luminance.

Table 3 shows measurements of luminescence characteristics of theorganic EL devices of Examples 21 and 22.

TABLE 3 1st 2nd LIGHT- LIGHT- LUMINOUS LIGHT EMISSION EMISSION EMITTEDEFFICIENCY WAVE- MAX DEVICE EMITTING ASSISTING ASSISTING COLOR (cd/A)LENGTH LUMINANCE STRUCTURE HOST DOPANT DOPANT DOPANT (CIEx, y) At100cd/m² (nm) (cd/m²) EX. 21 B Alq DCJTB DtBuPN TPD Red 2.1 634 14,000 x =0.65, y = 0.35 EX. 22 B Alq DCJTB DPN NPB Red 2.6 632 19,100 x = 0.65, y= 0.35

As shown in Table 3, the organic EL devices of Examples 21 and 22 bothprovided red light emission with high color purity. With the organic ELdevices of Examples 21 and 22, too, the addition of the secondlight-emission assisting dopant enhanced the luminous efficiency andmaximum luminance, as compared with those of the organic EL devices ofExamples 1-11. This shows that adding a second light-emission assistingdopant is effective in enhancing the luminous efficiency and maximumluminance. The organic EL devices of Examples 21 and 22, too, providedhigher luminous efficiency than the organic EL device of ComparativeExample 2. This shows that using rubrene derivatives as the firstlight-emission assisting dopants is effective in enhancing the luminousefficiency and maximum luminance also when TPD or NPB is used as asecond light-emission assisting dopant.

Table 4 shows measurements of luminescence characteristics of theorganic EL devices of Examples 23-28 and Comparative Examples 3-5.

TABLE 4 1st 2nd LUMINOUS LIGHT- LIGHT- EFFI- DEVICE LIGHT EMISSIONEMISSION EMITTED CIENCY WAVE- MAX STRUC- EMITTING ASSISTING ASSISTINGCOLOR (cd/A) LENGTH LUMINANCE TURE HOST DOPANT DOPANT DOPANT (CIEx, y)At100 cd/m² (nm) (cd/m²) EX. 23 C Alq DtBuPN — — Green 9.0 538 41,800 x= 0.30, y = 0.68 EX. 24 C Alq DPN — — Green 4.2 534 18,800 x = 0.29, y =0.62 EX. 25 C Alq DNN — — Green 5.8 540 23,000 x = 0.31, y = 0.65 EX. 26C Alq TNN — — Orange 6.8 578 45,400 x = 0.50, y = 0.49 EX. 27 C Alq DBzR— — Orange 4.6 585 26,000 x = 0.50, y = 0.49 EX. 28 C Alq DPyN — — Green4.1 541 25,700 x = 0.29, y = 0.68 Comparison 3 C Alq Coumarin 6 — —Green 3.5 538 18,000 x = 0.31, y = 0.66 Comparison 4 C Alq Rubrene — —Yellow 6.5 560 40,100 x = 0.49, y = 0.50 Comparison 5 C Alq DCM — —Orange 2.0 575 10,200 x = 0.53, y = 0.47

As shown in Table 4, the organic EL devices of Examples 23-28 providedluminous efficiencies of 4.1 to 9.0 cd/A, which are higher than those ofthe organic EL devices of Comparison Examples 3-5. This shows that usingthe rubrene derivatives as light emitting dopants, too, is effective inenhancing the luminous efficiency and maximum luminance.

Table 5 shows measurements of luminescence characteristics of theorganic EL devices of Examples 29-33.

TABLE 5 1st 2nd LIGHT- LIGHT- LUMINOUS LIGHT EMISSION EMISSION EMITTEDEFFICIENCY WAVE- MAX DEVICE EMITTING ASSISTING ASSISTING COLOR (cd/A)LENGTH LUMINANCE STRUCTURE HOST DOPANT DOPANT DOPANT (CIEx, y) At100cd/m² (nm) (cd/m²) EX. 29 D NPB DtBuPN — — Green 7.8 535 36,100 x =0.29, y = 0.67 EX. 30 D NPB DPN — — Green 3.6 532 27,700 x = 0.30, y =0.62 EX. 31 D NPB DNN — — Green 6.2 540 33,900 x = 0.30, y = 0.68 EX. 32D NPB TNN — — Yellow 9.0 570 40,500 x = 0.46, y = 0.53 EX. 33 D NPB DBzR— — Yellow 12.5 559 46,600 x = 0.49, y = 0.51

As shown in Table 5, the organic EL devices of Examples 29-33 providedhigh luminous efficiencies of 3.6 to 12.5 cd/A. This shows that usingthe rubrene derivatives as light emitting dopants with an electrontransporting layer replacing the hole transporting layer is alsoeffective in enhancing the luminous efficiency and maximum luminance.

Thus, it is seen from Examples 1-33 and Comparative Examples 1-5 thatusing the rubrene derivatives shown above as a light emitting dopant orfirst light-emission assisting dopant in a light emitting layer improvesluminous efficiency and luminance.

(2) Next, organic EL devices of Examples 34-108 were constructed andluminescence characteristics of these devices were measured.

Organic EL devices of Examples 34-40 have Device Structure E, organic ELdevices of Examples 41-67 have Device Structure F, organic EL devices ofExamples 68-94 have Device Structure G, and organic EL devices ofExamples 95-108 have Device Structure H.

Examples 34-40 used rubrene derivatives having molecular structures ofFormula (1a) below, among rubrene derivatives represented by Formula (1)shown earlier, rubrene derivatives having molecular structures ofFormula (2a) among rubrene derivatives represented by Formula (2), andrubrene derivatives having molecular structures of Formula (4a) amongrubrene derivatives represented by Formula (4).

In Formulas (1a), (2a) and (4a), Ar represents a substituent having anyof the structures represented by Formula (7a).

In Formula (7a), Y is O or S, R is a hydrogen atom, a halogen atom, or asubstituent, such as —H, —C_(n)H_(2n+1) (n=1-10), —OC_(n)H_(2n+1)(n=1-10), —N(C_(n)H_(2n+1))₂ (n=1-10), —X (X═—F, —Cl, —Br, or —I), —CN,a phenyl group, or a naphthyl group.

In particular, Compounds 1-27 having molecular structures of Formulas(C1)-(C27) below were used as materials of the light emitting layer.

(E) Device Structure E

In Device Structure E, a hole injecting electrode (anode), a holeinjecting layer, a hole transporting layer, a light emitting layer, anelectron transporting layer, and an electron injecting electrode(cathode) are sequentially stacked on a glass substrate.

In this case, the hole injecting electrode of the organic EL device hasa thickness of 1000 Å and is formed of indium-tin oxide (ITO). The holeinjecting layer has a thickness of 100 Å and is formed of copperphthalocyanine (hereinafter referred to as CuPc).

The hole transporting layer has a thickness of 500 Å and is formed ofNPB having the molecular structure of Formula (23) shown before.

The light emitting layer has a thickness of 400 Å, and contains, as ahost material, Alq having the molecular structure of Formula (24) above,and contains, as a red light emitting dopant, 2% of DCJTB having themolecular structure of Formula (25) above, and also contains, as alight-emission assisting dopant, 5% of a rubrene derivative, one ofthose shown above.

Examples 34-40 respectively used, as the light-emission assistingdopants, Compounds 1, 3, 7, 8, 16, 17 and 18 represented by Formulas(C1), (C3), (C7), (C8), (C16), (C17) and (C18).

The electron transporting layer is formed of Alq with a thickness of 100Å. The electron injecting electrode is formed of LiF/Al with a thicknessof 2000 Å.

(F) Device Structure F

In Device Structure F, a hole injecting electrode (anode), a holeinjecting layer, a hole transporting layer, a light emitting layer, anelectron transporting layer, and an electron injecting electrode(cathode) are sequentially stacked on a glass substrate.

In this case, the hole injecting electrode of the organic EL device hasa thickness of 1000 Å and is formed of indium-tin oxide (ITO). The holeinjecting layer has a thickness of 100 Å and is formed of CuPc.

The hole transporting layer has a thickness of 500 Å and is formed ofNPB having the molecular structure of Formula (23).

The light emitting layer has a thickness of 400 Å, and contains Alqhaving the molecular structure of Formula (24) as a host material, and5% of a rubrene derivative, one of the rubrene derivatives shown above,as a light emitting dopant.

Examples 41-67 respectively used Compounds 1-27 of Formulas (C1)-(C27)as the light emitting dopants.

The electron transporting layer is formed of Alq with a thickness of 100Å. The electron injecting electrode is formed of LiF/Al with a thicknessof 2000 Å.

(G) Device Structure G

In Device Structure G, a hole injecting electrode (anode), a holeinjecting layer, a hole transporting layer, a light emitting layer, anelectron transporting layer, and an electron injecting electrode(cathode) are sequentially stacked on a glass substrate.

In this case, the hole injecting electrode of the organic EL device hasa thickness of 1000 Å and is formed of indium-tin oxide (ITO). The holeinjecting layer has a thickness of 100 Å and is formed of CuPc.

The hole transporting layer has a thickness of 500 Å and is formed ofNPB having the molecular structure of Formula (23) shown above.

The light emitting layer has a thickness of 400 Å, and contains NPBhaving the molecular structure of Formula (23) as a host material, and5% of a rubrene derivative, one of those shown above, as a lightemitting dopant.

Examples 68-94 used Compounds 1-27 of Formulas (C1)-(C27) as lightemitting dopants.

The electron transporting layer is formed of Alq with a thickness of 100Å. The electron injecting electrode is formed of LiF/Al with a thicknessof 2000 Å.

(H) Device Structure H

In Device Structure H, a hole injecting electrode (anode), a holeinjecting layer, a hole transporting layer, a first light emittinglayer, a second light emitting layer, an electron transporting layer,and an electron injecting electrode (cathode) are sequentially stackedon a glass substrate.

In this case, the hole injecting electrode of the organic EL device hasa thickness of 1000 Å and is formed of indium-tin oxide (ITO). The holeinjecting layer has a thickness of 100 Å and is formed of CuPc.

The hole transporting layer has a thickness of 400 Å and is formed ofNPB having the molecular structure of Formula (23) shown above.

The first light emitting layer has a thickness of 100 Å, and contains,as a host material, NPB having the molecular structure of Formula (23),and contains, as a light emitting dopant(s), 2% (Examples 95-104) or 8%(Examples 105-108) of one or ones of rubrene derivatives shown above.

Examples 95-104 respectively used, as light emitting dopants in thefirst light emitting layer, Compounds 1, 1, 3, 7, 8, 16, 17, 18, 19 and20 of Formulas (C1), (C1), (C3), (C7), (C8), (C16), (C17), (C18), (C19)and (C20).

The second light emitting layer has a thickness of 300 Å, and contains,as a host material, diphenylanthracene having the molecular structure ofFormula (B2) and contains, as a light emitting dopant, 2% of perylene ofFormula (B3) shown earlier.

In Examples 105-108, in order to enhance the luminous efficiency ofwhite and to increase the half bandwidth of the spectrum to enhancecolor purity of white, the first light emitting layer was doped with twokinds of light emitting dopants: an orange-emitting rubrene derivativeand a green-emitting rubrene derivative.

Example 105 used Compound 1 of Formula (C1) and DtBuPN of Formula (A4)as light emitting dopants in the first light emitting layer. Example 106used Compound 1 of Formula (C1) and Compound 24 of Formula (C24) aslight emitting dopants in the first light emitting layer. Example 107used Compound 7 of Formula (C7) and Compound 25 of Formula (C25) aslight emitting dopants in the first light emitting layer. Example 108used Compound 9 of Formula (C9) and Compound 26 of Formula (26) as lightemitting dopants in the first light emitting layer.

The electron transporting layer is formed of Alq with a thickness of 100Å. The electron injecting electrode is formed of LiF/Al with a thicknessof 2000 Å.

A positive bias voltage was applied to the hole injecting electrode ofeach organic EL device and a negative bias voltage was applied to theelectron injecting electrode, and luminescence characteristics of thedevices were measured.

Table 6 shows measurements of luminescence characteristics of theorganic EL devices of Examples 34-40.

TABLE 6 LUMINOUS HOLE HOLE LIGHT- ELECTRON EMITTED EFFICIENCY WAVE- MAXINJECTING TRANSPORTING EMITTING TRANSPORTING COLOR (cd/A) LENGTHLUMINANCE EX. LAYER LAYER LAYER LAYER (CIEx, y) At100 cd/m² (nm) (cd/m²)34 CuPc NPB Alq + 2% Alq Red 3.9 638 24,000 DCJTB + 5% x = 0.65,Compound1 y = 0.35 35 CuPc NPB Alq + 2% Alq Red 3.7 639 21,000 DCJTB +5% x = 0.65, Compound3 y = 0.35 36 CuPc NPB Alq + 2% Alq Red 3.8 63823,000 DCJTB + 5% x = 0.65, Compound7 y = 0.35 37 CuPc NPB Alq + 2% AlqRed 3.2 638 19,000 DCJTB + 5% x = 0.65, Compound8 y = 0.35 38 CuPc NPBAlq + 2% Alq Red 3.8 638 23,000 DCJTB + 5% x = 0.65, Compound16 y = 0.3539 CuPc NPB Alq + 2% Alq Red 3.5 638 22,000 DCJTB + 5% x = 0.65,Compound17 y = 0.35 40 CuPc NPB Alq + 2% Alq Red 3.6 638 22,000 DCJTB +5% x = 0.65, Compound18 y = 0.35

As shown in Table 6, the organic EL devices of Examples 34-40 allprovided red light emission with high color purity. The organic ELdevices of Examples 39-40 provided high luminous efficiency and highmaximum luminance. This shows that the use of the rubrene derivatives aslight-emission assisting dopants is effective in enhancing the luminousefficiency and maximum luminance.

Tables 7 and 8 show measurements of luminescence characteristics of theorganic EL devices of Examples 41-67.

TABLE 7 LUMINOUS MAX HOLE HOLE LIGHT- ELECTRON EMITTED EFFICIENCY WAVE-LUMI- INJECTING TRANSPORTING EMITTING TRANSPORTING COLOR (cd/A) LENGTHNANCE EX. LAYER LAYER LAYER LAYER (CIEx, y) At100 cd/m² (nm) (cd/m²) 41CuPc NPB Alq + 5% Alq Orange-Yellow 8.5 583 39,900 Compound1 x = 0.51, y= 0.48 42 CuPc NPB Alq + 5% Alq Orange-Yellow 7.5 589 37,600 Compound2 x= 0.52, y = 0.47 43 CuPc NPB Alq + 5% Alq Orange-Yellow 8.5 583 39,700Compound3 x = 0.51, y = 0.48 44 CuPc NPB Alq + 5% Alq Orange-Yellow 6.8587 35,400 Compound4 x = 0.51, y = 0.48 45 CuPc NPB Alq + 5% AlqOrange-Yellow 5.5 579 32,100 Compound5 x = 0.50, y = 0.50 46 CuPc NPBAlq + 5% Alq Orange-Yellow 8.0 583 39,000 Compound6 x = 0.51, y = 0.4847 CuPc NPB Alq + 5% Alq Orange-Yellow 8.6 583 40,000 Compound7 x =0.51, y = 0.48 48 CuPc NPB Alq + 5% Alq Orange-Yellow 7.9 584 39,000Compound8 x = 0.51, y = 0.48 49 CuPc NPB Alq + 5% Alq Orange-Yellow 6.9570 33,300 Compound9 x = 0.50, y = 0.50 50 CuPc NPB Alq + 5% AlqOrange-Yellow 7.5 589 37,600 Compound10 x = 0.52, y = 0.47 51 CuPc NPBAlq + 5% Alq Orange-Yellow 6.5 579 34,000 Compound11 x = 0.51, y = 0.4852 CuPc NPB Alq + 5% Alq Orange-Yellow 8.5 583 39,700 Compound12 x =0.51, y = 0.48 53 CuPc NPB Alq + 5% Alq Orange-Yellow 8.0 580 39,000Compound13 x = 0.51, y = 0.48 54 CuPc NPB Alq + 5% Alq Orange-Yellow 7.9584 38,900 Compound14 x = 0.51, y = 0.48

TABLE 8 LUMINOUS MAX HOLE HOLE LIGHT- ELECTRON EMITTED- EFFICIENCY WAVE-LUMI- INJECTING TRANSPORTING EMITTING TRANSPORTING COLOR (cd/A) LENGTHNANCE EX. LAYER LAYER LAYER LAYER (CIEx, y) At100 cd/m² (nm) (cd/m²) 55CuPc NPB Alq + 5% Alq Orange-Yellow 7.9 584 39,000 Compound15 x = 0.51,y = 0.48 56 CuPc NPB Alq + 5% Alq Orange-Yellow 8.5 583 39,900Compound16 x = 0.51, y = 0.48 57 CuPc NPB Alq + 5% Alq Orange-Yellow 8.2584 39,700 Compound17 x = 0.51, y = 0.48 58 CuPc NPB Alq + 5% AlqOrange-Yellow 7.9 585 39,100 Compound18 x = 0.51, y = 0.48 59 CuPc NPBAlq + 5% Alq Orange-Yellow 8.0 581 39,000 Compound19 x = 0.51, y = 0.4860 CuPc NPB Alq + 5% Alq Orange-Yellow 8.0 585 39,500 Compound20 x =0.51, y = 0.48 61 CuPc NPB Alq + 5% Alq Green 11.0 537 45,000 Compound21x = 0.30, y = 0.64 62 CuPc NPB Alq + 5% Alq Green 9.8 536 41,000Compound22 x = 0.30, y = 0.64 63 CuPc NPB Alq + 5% Alq Green 8.9 53539,900 Compound23 x = 0.30, y = 0.64 64 CuPc NPB Alq + 5% Alq Green 11.0537 45,000 Compound24 x = 0.30, y = 0.64 65 CuPc NPB Alq + 5% Alq Green11.1 537 45,100 Compound25 x = 0.30, y = 0.64 66 CuPc NPB Alq + 5% AlqGreen 8.1 529 40,500 Compound26 x = 0.29, y = 0.65 67 CuPc NPB Alq + 5%Alq Red 2.0 648 11,000 Compound27 x = 0.65, y = 0.35

As shown in Tables 7 and 8, the organic EL devices of Examples 41-60provided orange-yellow light emission. The organic EL devices ofExamples 61-66 provided green light emission. The organic EL device ofExample 67 provided red light emission. The organic EL devices ofExamples 41-67 provided high luminous efficiency and high maximumluminance. This shows that using the rubrene derivatives as lightemitting dopants when Alq is used as the host material is effective inenhancing the luminous efficiency and maximum luminance.

Tables 9 and 10 show measurements of luminescence characteristics of theorganic EL devices of Examples 68-94.

TABLE 9 LUMINOUS MAX HOLE HOLE LIGHT- ELECTRON EMITTED EFFICIENCY WAVE-LUMI- INJECTING TRANSPORTING EMITTING TRANSPORTING COLOR (cd/A) LENGTHNANCE EX. LAYER LAYER LAYER LAYER (CIEx, y) At100 cd/m² (nm) (cd/m²) 68CuPc NPB NPB + 5% Alq Orange-Yellow 12.5 559 46,600 Compound1 x = 0.49,y = 0.51 69 CuPc NPB NPB + 5% Alq Orange-Yellow 9.6 572 38,800 Compound2x = 0.51, y = 0.48 70 CuPc NPB NPB + 5% Alq Orange-Yellow 10.1 56139,100 Compound3 x = 0.49, y = 0.51 71 CuPc NPB NPB + 5% AlqOrange-Yellow 9.0 570 37,200 Compound4 x = 0.51, y = 0.48 72 CuPc NPBNPB + 5% Alq Orange-Yellow 6.8 558 31,000 Compound5 x = 0.48, y = 0.5273 CuPc NPB NPB + 5% Alq Orange-Yellow 10.1 560 40,100 Compound6 x =0.49, y = 0.51 74 CuPc NPB NPB + 5% Alq Orange-Yellow 12.3 559 45,700Compound7 x = 0.49, y = 0.51 75 CuPc NPB NPB + 5% Alq Orange-Yellow 9.3561 37,800 Compound8 x = 0.50, y = 0.50 76 CuPc NPB NPB + 5% Alq Yellow7.8 555 33,000 Compound9 x = 0.47, y = 0.53 77 CuPc NPB NPB + 5% AlqOrange-Yellow 9.6 572 38,800 Compound10 x = 0.51, y = 0.48 78 CuPc NPBNPB + 5% Alq Orange-Yellow 7.8 562 33,100 Compound11 x = 0.49, y = 0.5179 CuPc NPB NPB + 5% Alq Orange-Yellow 11.1 563 42,000 Compound12 x =0.49, y = 0.51 80 CuPc NPB NPB + 5% Alq Orange-Yellow 10.0 564 39,900Compound13 x = 0.49, y = 0.51 81 CuPc NPB NPB + 5% Alq Orange-Yellow 9.3561 37,600 Compound14 x = 0.50, y = 0.50

TABLE 10 LUMINOUS MAX HOLE HOLE LIGHT- ELECTRON EMITTED EFFICIENCY WAVE-LUMI- INJECTING TRANSPORTING EMITTING TRANSPORTING COLOR (cd/A) LENGTHNANCE EX. LAYER LAYER LAYER LAYER (CIEx, y) At100 cd/m² (nm) (cd/m²) 82CuPc NPB NPB + 5% Alq Orange-Yellow 9.4 562 38,000 Compound15 x = 0.50,y = 0.50 83 CuPc NPB NPB + 5% Alq Orange-Yellow 12.5 559 46,500Compound16 x = 0.49, y = 0.51 84 CuPc NPB NPB + 5% Alq Orange-Yellow12.0 561 46,000 Compound17 x = 0.49, y = 0.51 85 CuPc NPB NPB + 5% AlqOrange-Yellow 11.5 560 43,400 Compound18 x = 0.49, y = 0.51 86 CuPc NPBNPB + 5% Alq Orange-Yellow 10.0 563 39,900 Compound19 x = 0.49, y = 0.5187 CuPc NPB NPB + 5% Alq Orange-Yellow 12.0 561 46,100 Compound20 x =0.49, y = 0.51 88 CuPc NPB NPB + 5% Alq Green 13.0 535 52,000 Compound21x = 0.29, y = 0.67 89 CuPc NPB NPB + 5% Alq Green 10.0 536 42,000Compound22 x = 0.29, y = 0.67 90 CuPc NPB NPB + 5% Alq Green 9.1 53438,200 Compound23 x = 0.29, y = 0.67 91 CuPc NPB NPB + 5% Alq Green 12.5535 50,100 Compound24 x = 0.29, y = 0.67 92 CuPc NPB NPB + 5% Alq Green12.0 535 47,000 Compound25 x = 0.29, y = 0.67 93 CuPc NPB NPB + 5% AlqGreen 9.8 539 38,500 Compound26 x = 0.30, y = 0.65 94 CuPc NPB NPB + 5%Alq Red 2.1 645 16,100 Compound27 x = 0.65, y = 0.35

As shown in Tables 9 and 10, the organic EL devices of Examples 68-87provided orange-yellow light emission. The organic EL devices ofExamples 88-93 provided green light emission. The organic EL device ofExample 94 provided red light emission. The organic EL devices ofExamples 68-94 provided high luminous efficiency and high maximumluminance. This shows that using the rubrene derivatives as lightemitting dopants when NPB is used as a host material is effective inenhancing the luminous efficiency and maximum luminance.

Table 11 shows measurements of luminescence characteristics of theorganic EL devices of Examples 95-108.

TABLE 11 HOLE IN- HOLE 1st 2nd ELECTRON LUMINOUS JECT- TRANS- LIGHT-LIGHT- TRANS- EMITTED EFFICIENCY WAVE- MAX ING PORT- EMITTING EMITTINGPORT- COLOR (cd/A) LENGTH LUMINANCE EX. LAYER ING LAYER LAYER LAYER INGLAYER (CIEx, y) At100 cd/m² (nm) (cd/m²) 95 CuPc NPB NPB +Diphenylanthracene + Alq White 15.0 489,560 66,000 2% Compound1 2%Perylene x = 0.35, y = 0.34 96 CuPc NPB NPB + Dianthrarylanthracene +Alq White 15.0 489,560 66,000 2% Compound1 2% Perylene x = 0.35, y =0.34 97 CuPc NPB NPB + Dianthrarylanthracene + Alq White 14.1 490,56061,000 2% Compound3 2% Perylene x = 0.35, y = 0.34 98 CuPc NPB NPB +Dianthrarylanthracene + Alq White 15.3 489,560 67,000 2% Compound7 2%Perylene x = 0.35, y = 0.34 99 CuPc NPB NPB + Diphenylanthracene + AlqWhite 12.0 489,563 49,800 2% Compound8 2% Perylene x = 0.35, y = 0.34100 CuPc NPB NPB + Dianthrarylanthracene + Alq White 15.6 489,560 68,0002% Compound16 2% Perylene x = 0.35, y = 0.34 101 CuPc NPB NPB +Dianthrarylanthracene + Alq White 14.5 489,561 62,000 2% Compound17 2%Perylene x = 0.35, y = 0.35 102 CuPc NPB NPB + Dianthrarylanthracene +Alq White 12.2 489,566 50,000 2% Compound18 2% Perylene x = 0.34, y =0.36 103 CuPc NPB NPB + Dianthrarylanthracene + Alq White 14.7 489,56862,000 2% Compound19 2% Perylene x = 0.35, y = 0.36 104 CuPc NPB NPB +Dianthrarylanthracene + Alq White 14.5 489,560 61,700 2% Compound20 2%Perylene x = 0.35, y = 0.34 105 CuPc NPB NPB + Dianthrarylanthracene +Alq White 16.1 490,560 73,000 5% Compound1 + 2% Perylene x = 0.33, 3%Compound94 y = 0.33 106 CuPc NPB NPB + 5% Dianthrarylanthracene + AlqWhite 16.5 490,560 75,000 Compound1 + 2% Perylene x = 0.33, 3%Compound136 y = 0.33 107 CuPc NPB NPB + 5% Dianthrarylanthracene + AlqWhite 16.2 490,560 73,000 Compound1 + 3% 2% Perylene x = 0.34,Compound137 y = 0.33 108 CuPc NPB NPB + 5% Dianthrarylanthracene + AlqWhite 16.0 490,560 72,000 Compound1 + 3% 2% Perylene x = 0.34,Compound138 y = 0.34

As shown in Table 11, the organic EL devices of Examples 95-108 providedwhite light emission. The organic EL devices of Examples 95-108 providedhigh luminous efficiency and high maximum luminance. This shows thatusing the rubrene derivatives as light emitting dopants in the firstlight emitting layer is effective in enhancing the luminous efficiencyand maximum luminance.

In particular, Examples 105-108 used two kinds of light emitting dopantsin the first light emitting layer: an orange-emitting rubrene derivativeand a green-emitting rubrene derivative, whereby the luminous efficiencyof white and the color purity of white were enhanced.

Thus, it was seen from Examples 34-108 that using the rubrenederivatives shown above as a light emitting dopant or light-emissionassisting dopant in a light emitting layer improves luminous efficiencyand luminance.

1. An organic electroluminescent device comprising: a hole injectingelectrode; an electron injecting electrode; and a light emitting layerprovided between said hole injecting electrode and said electroninjecting electrode, said light emitting layer containing a rubrenederivative5,12-bis(4-(6-methylbenzothiazole-2-yl)phenyl)-6,11-diphenylnaphthacenerepresented by Formula (A2)

.
 2. The organic electroluminescent device according to claim 1, whereinsaid light emitting layer contains a host material, a light emittingdopant, and a first light-emission assisting dopant, and said firstlight-emission assisting dopant is composed of said rubrene derivative.3. The organic electroluminescent device according to claim 2, whereinsaid light emitting layer further contains a second light-emissionassisting dopant.
 4. The organic electroluminescent device according toclaim 1, wherein said light emitting layer contains a host material anda light emitting dopant, and said light emitting dopant is composed ofsaid rubrene derivative.
 5. The organic electroluminescent deviceaccording to claim 2, wherein the content of said light emitting dopantis not less than 0.1 percent by weight nor more than 50 percent byweight, with respect to said host material.
 6. An organicelectroluminescent device comprising: a hole injecting electrode; anelectron injecting electrode; and a light emitting layer providedbetween said hole injecting electrode and said electron injectingelectrode, said light emitting layer containing a rubrene derivative5,6,11,12-tetrakis(4-tert-butylphenyl)-naphthacene represented by


7. An organic electroluminescent device comprising: a hole injectingelectrode; an electron injecting electrode; and a light emitting layerprovided between said hole injecting electrode and said electroninjecting electrode, said light emitting layer comprising, a first lightemitting layer that contains a compound having a molecular structurerepresented by Formula (C1), and a second light emitting layer thatcontains a luminescent material that emits blue light;


8. An organic electroluminescent device comprising: a hole injectingelectrode; an electron injecting electrode; and a light emitting layerprovided between said hole injecting electrode and said electroninjecting electrode, said light emitting layer comprising a first lightemitting layer that contains at least one compound selected from thegroup consisting of compounds having molecular structures represented byFormulas (C1)-(C20) and at least one compound selected from the groupconsisting of compounds represented by Formulas (A4)-(A7), (A10), and(C21)-(C27), and a second light emitting layer that contains aluminescent material that emits blue light;